1. Field of the Invention
The present invention relates to a novel, chemically amplified resist composition suited for use in micro-lithography.
2. Description of the Related Art
The miniaturization of a pattern rule has been demanded in order to cope with a recent tendency of LSI technology to higher integration and higher speed. Under such a circumstance, far ultraviolet lithography has been regarded promising as the next-generation of micro-lithography. Even a pattern of 0.3 μm or less can be formed by far ultraviolet lithography, and use of a resist material exhibiting low light absorption makes it possible to form a pattern with side-wall angles nearly vertical to a substrate. In recent years, a technique making use of a high intensity KrF excimer laser as a far-UV light source has drawn attentions. There is accordingly a demand for the development of a low light absorbing and highly sensitive resist material which permits the use of the above-described technique for mass production.
From such a viewpoint, the recently-developed, chemically amplified positive type resist materials as described in Japanese Patent Publication (JP-B) No. 2-27660/'90 and Japanese Patent Provisional Publication (JP-A) No. 63-27829/'88 using an acid catalyst are particularly promising resist materials suited for far-UV lithography, because of their excellent characteristics such as high sensitivity, resolution and dry etching resistance.
Prior-art chemically amplified resists are however accompanied with the problems such as PED (Post Exposure Delay) that line patterns have a T-top profile, in other words, patterns become thick at the top, when the dwelling time from exposure to PEB (post exposure bake) is extended; and a so-called “trailing phenomenon” that patterns in the vicinity of a basic substrate, particularly, a substrate made of silicon nitride or titanium nitride are widened.
It is presumed that the T-top profile results from lowering in the solubility of the surface of a resist film, while the trailing phenomenon on a substrate results from lowering in solubility in the vicinity of the substrate.
In addition, during the time from exposure to PEB, a dark reaction for eliminating an acid-labile group proceeds, leading to a problem that the leaving size of the line of a positive resist decreases.
These problems are serious hindrance to practical use of the chemically amplified resist. Such problems of the conventional chemically amplified positive resist material not only make difficult dimensional control upon lithography but also impair dimensional control upon processing of a substrate by using dry etching [refer to: W. Hinsberg, et al., J. Photopolym. Sci. Technol., 6(4), 535-546(1993) and T. Kumada, et al., J. Photopolym. Sci. Technol., 6(4), 571-574(1993)].
It is understood that in these chemically amplified positive type resist materials, a basic compound in the air or on the surface of a substrate largely takes part in the problem of PED or trailing phenomenon on the substrate. An acid on the surface of a resist film generated by exposure to light reacts with a basic compound in the air and is thereby deactivated. The longer the dwelling time from exposure to PEB becomes, the more the amount of a deactivated acid increases, making it difficult to cause decomposition of an acid-labile group. An insolubilized layer is therefore formed on the surface and a pattern inevitably has a T-top configuration.
It is well known that addition of a basic compound is effective for overcoming PED, because it can suppress the influence of a basic compound in the air (as described in Japanese Patent Provisional Publication Nos. 5-232706/'93, 5-249683/'93, 5-158239/'93, 5-249662/'93, 5-257282/'93, 5-289322/193, 5-289340/'93, 6-194834/'93, 6-242605/'94, 6-242606/'94, 6-263716/'94, 6-263717/'94, 6-266100/'94, 6-266111/'94, 7-128859/'95, 7-92678/'95, 7-92680/'95, 7-92681/'95, 7-120929/'95 and 7-134419/'95).
As the basic compound, a nitrogen-containing-compound is well known and examples include amine compounds and amide compounds having a boiling point of 150° C. or greater. Specific examples include pyridine, polyvinyl pyridine, aniline, N-methylaniline, N,N-dimethylaniline, o-toluidine, m-toluidine, p-toluidine, 2,4-lutidine, quinoline, isoguinoline, formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, 2-pyrrolidone, N-methylpyrrolidone, imidazole, α-picoline, β-picoline, γ-picoline, o-aminobenzoic acid, m-aminobenzoic acid, p-aminobenzoic acid, 1,2-phenylenediamine, 1,3-phenylenediamine, 1,4-phenylenediamine, 2-quinolinecarboxylic acid, 2-amino-4-nitrophenol, and triazine compounds such as 2-(p-chlorophenyl)-4,6-trichloromethyl-s-triazine. Among them, pyrrolidone, N-methylpyrrolidone, o-aminobenzoic acid, m-aminobenzoic acid, p-aminobenzoic acid and 1,2-phenylenediamine are typical examples.